Computer supported circuit simulation has become an indispensable tool in electronic circuitry design to save on time and costs. An aspect of circuitry behaviour that can be modeled is related to electromagnetic compatibility (EMC). EMC is concerned with the circuit's susceptibility to irradiation, crosstalk and emission of radiation. A device is susceptible to irradiation when an incoming electromagnetic field induces currents in the circuit's conductors. Crosstalk occurs when a current in a particular conductor of the circuit gives rise to an inductively or capacitively induced current in another conductor of the circuit. Emission of electromagnetic radiation takes place when a current in a conductive portion of the circuit produces an electromagnetic field that may be picked up by another circuit or system.
In the design of electronic systems, the electromagnetic field concept is replaced by an electric circuit concept. This implies that the electromagnetic field in the electronic system is locally specified in terms of currents and voltages that comply with Kirchhoff's laws. These currents and voltages can be thought of as originating in a dynamically equivalent circuit made up of lumped components such as resistors, capacitors and inductances. Such an equivalent circuit model is created below for a conductor pattern. The actual pattern of conductors of e.g., printed circuit boards (PCBs), antennae, ICs, multi-chip modules (MCMs), leadframes, etc, is translated into a model of virtual equivalent electrical circuit in terms of virtual parts (resistors, capacitors, inductances and voltage sources) that are interconnected via nodes. This equivalent model is thereupon supplied to a circuit simulator, together with circuit models of the actually used electrical or electronic components (i.e., those which in reality are to be soldered onto the PCB) to produce information regarding the actual currents and voltages (throughout the PCB) for investigating the radiation behaviour. The conductors may include wires, whose radii are small compared to the wavelength of the radiation in the surrounding medium and small compared to its length, and planar conductive structures, which are embedded in a dielectric and whose thickness is small compared to the wavelength and to both length and width of the structure. The parameter values of the virtual parts making up the equivalent circuit are obtained as follows. First, the lay-out of the conductors is divided into a plurality of non-overlapping, contiguous geometrical elements, each whereof has a size smaller than a predetermined upper bound. This upper bound depends on, for example, the geometrical details and shapes involved. Element generating algorithms or meshing algorithms are well known in the art. An example of such an algorithm is the Delauney algorithm that divides a planar geometrical domain into triangular elements.
For the collection of the geometrical elements, a discretisized version of Maxwell's differential/integral equations is created in the form of matrix-vector equations, e.g., according to the Boundary Element Method. For the Boundary Element Method, see, e.g., "Field Computation By Moment Methods", R. F. Harrington, Macmillan, N.Y., 1968. The matrices contain terms that eventually can be translated into parameter values of the virtual components of the equivalent circuit by correlation to a Norton multi-port model. Typically, the number of virtual components of the equivalent circuit determined according to above prior art model lies in the order of a billion (10.sup.9) or more, i.e., of the square of a characteristic number of geometrical elements. The computation time, needed when simulating the behaviour of the electronic device using the equivalent circuit model, and the number of virtual components are strongly correlated. The state of the art method discussed above renders simulations of larger PCBs, such as computer cards, practically unattainable owing to the massive amount of data involved in the geometrical details of a realistic pattern and hence to the huge numbers of virtual components that are to be taken into account.